U.S. Pat. No. 3421326 of Henri Vidal describes earth structures including retaining wals wherein stability is achieved by compacting successive layers of earth into frictional contact with stabilising members. In this way, the frictional forces between the stabilising members and the adjacent earth particles, and between the earth particles themselves, resist failure caused by lateral earth movement and the resulting tensile forces in the stabilising members, which inevitably have some measure of elasticity, permit slight elastic deformation of the stabilised earth mass thereby enhancing its stability. This technique enables retaining walls for embankments and the like to have at least one substantially vertical face and such a face will normally be clad with a facing system which, in order to conform to small movements created by the above compacting procedure and to accommodate the small elastic or even permanent movements of the structure permitted by the stabilisation technique, are preferably flexible in the plane of the face. In general, such flexibility can be provided by facing panels attached to the stabilising members which are arranged accurately to terminate at the vertical face concerned.
Such panel facing systems provide a high level of architectural finish and satisfactorily resist erosion of the earth of the retaining wall. However, there is a general demand in respect of all retaining wall systems for architectural effects involving growing plants which not only provide an attractive, softer surface appearance but may also serve to absorb sound in urban traffic environments and at airports.
Such systems contrive to provide areas of exposed earth in an otherwise fully clad facing, commonly by incorporating box-like sections into the wall or by constructing a caisson-type gravity wall with exposed earth areas. However, such walls tend to use significantly more reinforced concrete or similar materials than a conventional flat facing, particularly the relatively thin facing systems used in the frictional stabilising technique described above.